Accelerator of vulcanization



Patented May 6, 1930 UNITED STATES PATENT OFFICE IAN TEPIEEMA, OF AKRON, OHIO, ASSIGNOE TO THE GOODYEAR TIRE & RUBBER COM- PANY, OF AKRON, OHIO, A CORPORATION OF OHIO Y ACCELERATOR OF VU'LCANIZATION No Drawing.

My invention relates to the treatment of rubber and it has particular relation to a method whereby the vulcanization of a rubber tion of rubber compounds which is composed of the reaction product of a 2-halogen thiazole and its substitution products, and an organic sulphide. 7

It has been observed heretofore that certain thiazole compounds, for example mercaptobenzothiazole, whose structural formula may berepresented as follows:

when incorporated into a vulcanizable rubber compound-greatly accelerates the rate of vulcanization of the latter. The product resulting from the practice of this process has ahigh degree of tensile strength and elasticity.

This invention consists in the discovery that certain thiazole compounds, for exampleQ- chlor benzothiazole having the structural formula:

in which R represents a halide, may be Application filed December 10, 1927. Serial No. 239,266.

caused toreact with alkali salts of organic sulphides, for example, the sodium salt of diethyl dlthiocarbamate, to produce a material having excellent properties as an accelerator when incorporated in rubber compounds.

The first mentioned material (Q-chlor benzothiazole) may be conveniently prepared by the following method: A i

Dissolve 200 parts of crude mercaptobenzothiazole in 400 parts of pentachlorethane and then bubble chlorine gas through this solution for a period of several hours while the solution is being heated under a reflux con denser. Chlorination should continue preferably from five to seven hours, although this period may beshortened or increased somewhat at the will of the operator. However, the longer periods of chlorination result in a more complete reaction. The reaction product is then distilled and the fraction boiling at a temperature of 240 to 252 is separated from the remainder and represents the major portion of the reaction product of chlorine and mercapto-benzothiazole.

The 2-chlor benzothiazole prepared by the preceding method may be caused to react with various dithiocarbamates toproduce excellent accelerators for rubber compounds.

The reaction product of 2-chlor benzothiazole and the sodium salt of diethyl dithiocarbamate is an example of a material of this class which has been found to be very eflicient. The following method may be employed in the manufacture of this material.

Dissolve 133 grams of 2-chlor benzothiazole and 120 grams of sodium diethyl dithiocarbamate in 500 cc. of ethyl alcohol and reflux the solution for a period of six hours. The alcohol is then distilled ofi preferably under a reduced pressure and the reaction product remaining in' the form of a residual oil is washed with water. The material may then bev dried with anhydrous calcium chloride (CaCl and filtered. The oil when distilledat a pressure of five mm, of mercury yields a light yellow oil which is a non-accelerator and a resinous residue which is an accelerator.

The invention is not limited to the reaction product of 2-chlor, benzothiazole with the alkali salts of dithiocarbamates, but it also includes the substituted chlor-thiazoles; for example, 6-nitro 2-chlor benzothiazole may be caused to react with diethyl dithiocarbamate by the following method:

Dissolve 35 grams of 6-nitro 2-chlor benzothiazole in alcohol and heat the solution to boiling and then add 30 grams of sodium diethyl (lithiocarbamate. After the solution has boiled for a period of five to ten minutes,

it solidifies as a yellow mass. Thevessel containing the mass is exposed to the heat of a small flame for a period of an hour and is then cooled. The reaction product precipitates as a crystalline material which should be washed with water to remove any sodium chloride formed during the reaction. The crystalline material may be further purified by recrystallizing it from boiling alcohol from which it precipitates in form of yellow needles having a melting point of 120 to 122 degrees C.

The invention also includes the reaction products of halogenated thiazoles with various dithiocarbamates other than diethyl dithiocarbamate. Specific examples of these materials are the reaction products of chlor benzothiazoles with the salts of piperydyl dithiocarbamates (semi-solid oily substances), the reaction product of chlor benzothiazole with sodium dibenzyl dithiocarbamate (a dark oily material), the reaction product of sodium piperydyl dithiocarbamate with 2 chlor 6-nitrobenzothiazole (a crystalline substance having a melting point of 151155 v C.) and the reaction product of sodium dibenzyl dithiocarbamate with 2-chlor 6-nitrobenzothiazole (a light yellow solid having a melting point of 141-142" 0.).

All of these materials may be prepared by methodsisimilar to those employed in the preparation of the reaction product of 2- chlor benzothiazole and diethyl dithiocarbamate. The compounds so prepared may be employed as accelerators in most of the standard rubber compounds. The following is an example of a formula which insures excellent results when any of the substances above mentioned are employed as accelerators.

Parts Extracted rubber 100- Zinc oxide 5 Sulphur 3v Stearic acid 1.5 Accelerator .5

Samples of these materials were subjected to vulcanization by steam heat in a mold and the samples after vulcanization were subjected to physical tests to ascertain their yield and tensile strength. The results of these tests are contained in the following tables:

Reaction product 2-chlor benzothiazole sodium (11 ethyl dithiocarbamatc Load in Tensile kgsJcm. Per cent Cure strength Reaction product 2-chlor G-nitrobcnzothincole and sodium diethyl dithiocarbnmoie Reaction product of sodium piperydyl dithiocmbm mate and Q-chlor bcncofhiacolc Load in kgsJemJat Tensile Cure strength 5 23 n 500% 100% lags/cm? eiong elong Reaction product sodium rlibcncyl dithiovm'bumllfc and. 21-1110) bcnzothiusolc Reaction product sod-tum pipcrydyl (lithioccrbamulv and Q-chlm (I-nitro licnc'oi'iiiucoic Load in kgsJcmJ at Tensile ,Curestrength Percent 700% ligsJcm. elong. along. along.

Reaction product sodiumdibenzyl dithiocarlm'mflic and 2-olilor G-nitro bencotliiazolc Load in k gsJcmJat T 1 611818 Cure strength z g g 300% 500% lqzsJcm. elong. clung.

' It will be apparent from the preceding tables that the use of these accelerators results in rapid cures at comparatively low temperatures and the vulcanized product has excellent physical properties both w th regard to tensile str'ength and elongation.

In the preceding examples specific reference has been made only to the reaction products'of 2-chlor benzothiazoles with the sodium salts of the dithiocarbamates. However, the bromobenzothiazoles may be substituted forv the chlor thiazoles and the potassium or other salts of the dithiocarbamates may be substituted in lieu of the sodium salt.

Although I have described in detail only the preferred embodiments of the invention, it will be apparent to those skilled in the art that it is not so limited but that various minor modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What I claimis:

1. A method of treating rubber compounds which comprises vulcanizing the compounds in the presence of the reaction product of a 2-halogen benzothiazole and a dithiocarbamate.

2. A method of treating rubber compound which comprises vulcanizing the compounds in the presence of a material having the following structural formula in which R represents an aryl group and R represents a dithiocarbainate group, said material being an accelerator of the rate of vulcanization of the rubber.

3. A method of treating rubber compounds which comprises vulcanizing the compound in the presence of a material having the following structural formula in which R represents an aryl group and R represents a dithiocarbamate group.

4. A methodof treating rubber compounds which comprises vulcanizing them in the presence .of a material prepared in accordance with the following reaction:

in which R represents an aryl group, R

represents a halogen group, M represents an O.NUS\O B N in which R represents a dithiocarbamate group.

7. A method of treating rubber compounds which comprises vulcanizing them in the presence of the reaction product of a nitro- 2-chlor benzothiazole and an alkali salt of a dithiocarbamate.

8. A method of treating rubber compounds which comprises vulcanizing them in the presence of the reaction product of a nitro 2-halog en substituted benzothiazole and an alkali salt of diethyl dithiocarbamate.

9. A method of treating rubber compounds which comprises vulcanizing them in the presenceof the reaction product of 6-nitro 2-ch1or benzothiazole and the sodium salt of diethyl dithiocarbamate. V

10. A rubber product that has been vulcanized in the presence of the reaction product of a 2-halogen substituted benzothiazole and an alkali salt of a dithiocarbamate.

11. A rubber product that has been vulcanized in the presence of a material having the following structural formula:

in which represents an aryl group and R represents a dithiocarbamate group.

12. A rubber product that has been vulcanized in the presence of a material that has been prepared in accordance with the following equation:

in which R represents a benzene group, R represents a halogen group, M represents an alkali metal and R represents a dithiocarbamate group.

13. A rubber product that has been vulcanized in the presence of a material formed by the interaction of a substance having the. following structural formula R Z CRl and a substance having the formula in which R represents a benzene group, R

. s C] B ai i s in which R represents an aryl group.

16. A rubber product which has been vulcanized in the presence of a material having the following structural formula:

in which R represents an aryl group.

17. A method of treating rubber which comprises subjecting it to vulcanization inv the presence of a material having the following structural formula:

S C2H5 S 01H) NQ.

18. A method of treating rubber which comprises subjecting it to vulcanization in the presence of a material having the following structural formula:

in which R represents an aliphatic amine group and R represents an aryl group.

19. A method of treating rubber which comprises subjecting it to vulcanization in the presence of a material having the following structural formula in which R represents an aliphatic amine group and R represents a benzene nucleus.

20. A rubber product that has been vulcanized in the presence of a material having the following structural formula:

in which R represents an amine group and R represents an aryl group.

21. A rubber product that has been vulcanized in the presence of a material having the following structural formula:

in which R represents an amine group and R represents a benzene nucleus.

In witness whereof, I have hereunto signed my name at Akron, in the county of Summit,

and State of Ohio, this 8th day of December,

JAN TEPPEMA. 

